Pulsator diaphragm



Oct. 5, 1965 J. F. WALDHERR 3,209,700

PULSATOR DIAPHRAGM Filed Oct. 15, 1963 INVENTOR. dorm WALDHERR ATT ORN EY United States Patent M 3,209,700 PULSATOR DIAPHRAGM John F. Waldherr, Fond du Lac, Wis., assignor to Wells Manufacturing Corporation, Fond du Lac, Wis., a corporation of Wisconsin Filed Oct. 15, 1963, Ser. No. 316,409 1 Claim. (Cl. 103-150) This invention relates to fuel pumps of the diaphragm type which are generally employed with internal combustion engines. Since the diaphragm action inherently tends to produce a pulsative or non-uniform pressure in the dicharge of the fuel, pumps of this type have usually been provided with a pulsator diaphragm which forms a resilient wall between the pumps discharge chamber and a pulsator chamber to thereby define an air cushion which exerts a stabilizing effect on the pump discharge pressure and flow. Specifically, the invention relates to an improved pulsator diaphragm for this type of fuel pump.

Several of the conventional fuel pump designs provide a pulsator diaphragm which is pressed or squeezed between two mating parts of the fuel pump assembly (usually between a pulsator cap and the fuel pump housing) with the pressure between such parts being the sole means of retaining the diaphragm in operative position. In such instances the pulsator also acts as a seal between the two parts. I have discovered an inherent weakness in this type of fuel pump, i.e., the possibility of fuel pump failure by virtue of the pulsator diaphragm being pulled out from between the mating fuel pump parts, thereby causing fuel leakage and inoperativeness of the pump. My investigation has revealed that normal warpage of the die cast fuel pump components in combination with the relatively high pressures built up in the discharge chamber after the shut off of an automobile engine is the cause of the above described failure.

In particular, I have discovered that the discharge chamber pressure after engine shut-off reaches a level of about four times the normal operating pressure. This increase is attributable to the fact that at this time both the needle valve of the carburetor and the outlet valve of the fuel pump hold pressure, thereby permitting the increase of the under-the-hood temperature to expand the fuel within the discharge chamber. At these times, the pulsator diaphragm deflection is also correspondingly increased, and only a relatively slight warpage of the fuel pump assembly or one of it parts is enough to sufficiently reduce the holding force exerted on the pulsator diaphragm and to permit the same to be pulled out from its operative position.

To avoid the above described failure, I have provided the pulsator diaphragm with a lip which is so contoured as to resist the inward pull exerted during the pressure build up within the discharge chamber and thereby avoid the heretofore described failure without any changes in or addition of components to the present fuel pump design.

In view of the above, the principal object of this invention is to provide a pulsator diaphragm which will eliminate the above described fuel pump failure without changing the present fuel pump design and without the addition of new parts to the fuel pump.

Other objects and advantages will be pointed out in, or be apparent from, the specification and claim, as will obvious modifications of the single embodiment shown in the drawings, in which:

FIG. 1 is a schematic view, part in cross section, of a conventional fuel pump equipped with a pulsator diaphragm embodying the present invention;

FIG. 2 is a cross sectional view taken on line 2-2 of FIG. 3 of the pulsator diaphragm embodying the present invention;

3,209,700 Patented Oct. 5, 1965 FIG. 3 is a plan top view of the pulsator diaphragm shown in FIG. 2;

FIG. 4 is a plan bottom view of the pulsator diaphragm shown in FIG. 2; and

FIG. 5 is a fragmentary cross sectional view of the pulsator diaphragm and fuel pump parts showing the manner of securing the diphragm within the pump.

Referring to the drawings in detail, the fuel pump shown in FIG. 1 is of the conventional design and particularly of the type illustrated in Harry Patent No. 2,929,333 issued on March 22, 1960. The fuel pump is generally comprised of a die cast housing 10 having a threaded inlet 12 and outlet 14 communicating with inlet and outlet chambers 16 and 18 respectively. Below the two aforementioned chambers is a pumping chamber 20 which communicates with the chambers 16 and 18 by means of ports 22 and 24 which are provided with one-way inlet and discharge valves 26 and 28 respectively. The pumping chamber 20 is defined by a pumping diaphragm 30 which is connected by a shaft 32 to the engine cam shaft 33 for actuation thereby.

A pulsator diaphragm 34, made of synthetic rubber or a similar resilient material, is positioned in an overlying relationship in respect to the discharge chamber 18 and defines with the pulsator cap 36 an air cushion or pulsator chamber 38 which exerts the required stabilizing effect upon the fuel discharge. The peripheral portion 39 of the pulsator diaphragm is provided with a groove 40 which divides the peripheral portion into inner and outer sections, the outer section forming an outer lip 42 having a circumferentially and radially inwardly facing surface. A bolt 44 threadably received in central bushing 46 of the housing presses the pulsator diaphragm in sealing engagement between the flange 45 of the pulsator cap and flange 47 of the fuel pump housing, the latter engaging the groove 40 and thereby rendering the lip 42 capable of resisting any inward pull which results at the times of pulsator diaphragm expansion. The pulsator diaphragm is provided with a suitable aperture 48 for receiving bolt 44 and a recessed central portion 50 for receiving the end of the bushing 46.

The pulsator diaphragm is also provided with radially extending ribs 52 which are of the same thickness as the peripheral portion 39 and which define segments 54 of substantially smaller thickness between adjacent ribs. This feature provides sufficient resistance to the excessive pressures and diaphragm deflection at times of engine shutoif, yet renders the diaphragm sufiiciently flexible during operation of the fuel pump to provide the desired stabilizing effect.

Although the invention has been illustrated as applied to a specific type of fuel pump, it should be apparent that the same invention is equally applicable to any fuel pump which employs a pulsating chamber and a pulsating diaphragm. Further, it should be noted that the groove 40 could equally well be on the pulsator chamber side if such construction would be thought more desirable from a manufacturing or design standpoint.

Although but a single embodiment of the present invention has been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claim.

I claim:

A fuel pump having a discharge chamber and a pulsating chamber, said chambers being separated by a pulsating diaphragm which is clamped between two mating parts of the fuel pump, said pulsating diaphragm comprising a flat piece of resilient material having a peripheral portion which is thicker than the average diaphragm thickness and having a plurality of ribs on one face of said flat piece, said ribs extending radially inwardly from said peripheral portion and defining a plurality of diaphragm segments of less diaphragm thickness than said ribs and peripheral portion, a groove in One face of said fiat piece, said groove being located in said peripheral portion and separating said peripheral portion into inner and outer sections, said groove being engaged by one of the mating parts, said outer section forming a lip which is engaged on its circumferentially and radially inwardly facing surface by the other of the mating parts to prevent said diaphragm from being pulled out at times of high pressure Within said discharge chamber.

References Cited by the Examiner UNITED STATES PATENTS 2,283,439 5/42 Herman.

2,529,204 11/50 Van Ranst et a1. 103150 2,779,353 1/57 Coffey 103223 X FOREIGN PATENTS 912,031 12/62 Great Britain. 1,303,475 4/62 France.

DONLEY J. STOCKING, Primary Examiner.

WARREN E. COLEMAN, Examiner. 

